The hierarchical structure of a device for resistance welding is described in German Published Patent Application No. 101 14 323 (see, e.g., FIG. 3). With the aid of a rectified, three-phase a.c. power supply, a.c. voltages of variable phase and frequency are generated for the power supply of the welding clamp and the drives. For this purpose, the welding inverter provides a two-phase output voltage and the drive inverter a three-phase output voltage.
The foregoing is believed to be practical for supplying components within a single unit, but not for bridging greater distances and for supplying several autonomous resistance welding systems, e.g., welding robots within a production line in the automotive industry. Moreover, a new inversion using a relatively complex circuit configuration may be required for generating the welding current. This may entail a greater space requirement.